Catheters are commonly used for a wide variety of purposes including draining fluids from and introducing fluids to the body. In certain cases, a catheter may be semi-permanently placed to form a path to and from the body for repeated fluid transfers.
Several problems commonly associated with placing foreign elements such as catheters within the body for extended periods are not easily solved. In the case of a permanently or semi-permanently placed catheter, for example, biological materials may form occlusions or partial blockages within the catheter lumen. For example, blockages may be formed by precipitates from fluids flowing through the catheter or, for catheters through which blood is to flow, a blood clot or fibrin buildup may accumulate in the lumen.
In addition, the flow through a catheter may be reduced or completely blocked by mechanical constriction of the lumen. For example, kinks may form in the catheter as the patient moves about or because of imperfect placement of the catheter. If the catheter is bent along a radius of curvature smaller than a critical radius, the catheter's lumen may collapse significantly reducing its cross-sectional area. Clearing an occlusion or removing a mechanical constriction of a lumen of an implanted catheter may entail removing the catheter and replacing it.
To prevent lumen collapse during insertion, conventional catheters are often constructed of materials which have inherently good column strength. However, the catheters formed by these materials may lack other desirable qualities. For example, softer catheters which permit increased patient mobility may be avoided in favor of stiffer catheters (i.e., catheters with higher column strengths) which more effectively resist lumen collapse.